package com.zkgengkun.support.snowflake;

public class IdWorkerFromSnowflake implements IdWorker {

    public final static String MYID = "2";//短链接生成

    private long workerId;
    private long datacenterId;
    private long sequence = 0L;
    private long twepoch = 1288834974657L;
    private long workerIdBits = 5L;
    private long datacenterIdBits = 5L;
    private long maxWorkerId = -1L ^ (-1L << workerIdBits);
    private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    private long sequenceBits = 12L;
    private long workerIdShift = sequenceBits;
    private long datacenterIdShift = sequenceBits + workerIdBits;
    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private long sequenceMask = -1L ^ (-1L << sequenceBits);
    private long lastTimestamp = -1L;

    public IdWorkerFromSnowflake() {
    }

    public IdWorkerFromSnowflake(long workerId, long datacenterId) {
        // sanity check for workerId
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format(
                    "worker Id can't be greater than %d or less than 0",
                    maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format(
                    "datacenter Id can't be greater than %d or less than 0",
                    maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    public synchronized long nextId() {
        long timestamp = timeGen();
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(
                    String.format(
                            "Clock moved backwards.  Refusing to generate id for %d milliseconds",
                            lastTimestamp - timestamp));
        }

        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }
        lastTimestamp = timestamp;
        return ((timestamp - twepoch) << timestampLeftShift)
                | (datacenterId << datacenterIdShift)
                | (workerId << workerIdShift) | sequence;
    }

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    protected long timeGen() {
        return System.currentTimeMillis();
    }

    public synchronized long nextId(long workerId, long datacenterId) {
        // sanity check for workerId
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format(
                    "worker Id can't be greater than %d or less than 0",
                    maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format(
                    "datacenter Id can't be greater than %d or less than 0",
                    maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;

        return this.nextId();
    }

    public long nextId(long dataId) {
        // return this.nextId((long) Math
        // .ceil(dataId % 32 > 0 ? dataId % 32 - 1 : 0),// 计算workerId，范围从0到31
        // (long) Math.ceil(dataId / 32 > 0 ? dataId / 32 - 1
        // : 0)// 计算datacenterId，范围从0到31
        // );
        /*
         * 由于某些同学提出的问题 使用纯数据源的主键生成方式可能会有重复 尽管概率非常的低
		 * 目前改为纯采用雪花的原生算法计算支持32台主机乘以32台数据库的支持
		 */
        return this.nextId((long) Integer.valueOf(MYID) - 1, (long) dataId - 1);
    }
}
